A banned jihadi charity accused of links to November's Mumbai attacks has resurfaced in north-western Pakistan, where it is running an extensive aid programme for people fleeing fighting in Swat.

The Falah-i-Insaniat Foundation (FIF) offers food, medical care and transport to villagers fleeing into Mardan district, where authorities are struggling to cope with an influx of more than 500,000 people.

But the charity, according to experts, officials and some of its own members, is the renamed relief wing of Jamaat-ud-Dawa, a group the Pakistani government banned last December after the UN declared it a terrorist organisation.

Jamaat-ud-Dawa is considered to be the public face of Lashkar-e-Taiba, the militant group accused of orchestrating the Mumbai attack on hotels and cafes that killed at least 173 people.

The Pakistan government declared a crackdown on Jamaat-ud-Dawa, closing dozens of offices and placing the leadership under arrest, but during the past 12 days its volunteers have re-emerged under their new name on the frontline of aid efforts.

The first relief camp is located outside Sher Gur in Mardan, just a few hundred metres from the border with Malakand, the mountainous area comprising Swat, Dir and Buner where the fighting is concentrated.

On Tuesday evening a stream of trucks, tractors and even rickshaws, all loaded with war-weary refugees, was met by roadside volunteers offering water, fruit juice and plates of steaming hot rice.

The vehicles were marshalled into the camp by a bearded man waving a black-and-white flag depicting a long sword and the Kalma, the Islamic article of faith – the same as the Jamaat-ud-Dawa standard.

Also present was Hafiz Abdur Rauf, head of the FIF and the former head of Jamaat-ud-Dawa's welfare wing. In a rare interview, he described the charity's expansive programme.

The group's 24-hour kitchens had fed 53,000 people in roadside camps and in schools where people were living, he said. A fleet of 23 minibuses transported victims from the battle zone while seven ambulances took the injured to hospital.

It offers to pay bus fares for people fleeing to cities such as Lahore and Karachi, and is organising emergency lodgings in madrasas for those remaining behind. It intends to build two tented camps catering for 3,000 displaced families in the coming month.

A serious young man with a scraggly beard, Rauf was visiting from his Lahore headquarters. He arrived in a new saloon car accompanied by several burly men.

"People are very afraid and worried about what's going on. They are terrified by the shelling and the bombardment, especially the children," he said, as volunteers stirred six large pots of food behind him.

He was careful to avoid direct criticism of either the army or the Taliban. "We have no political aims or agenda," he said. He also skirted questions about the link with Jamaat-ud-Dawa, saying when pressed that it was "a different organisation".

But in nearby Mardan city several people, including a member of his own organisation, said otherwise.

At a major traffic junction, bearded activists manned a fundraising tent festooned with FIF signs and the group's distinctive black and white flags. "Stop the killing of Muslims," read a sign in Urdu, with blood dripping from its letters.

"The old name was Jamaat-ud-Dawa; this is the new one," said Amjad Ali, a 34-year-old trader who described himself as a spokesman. He said the organisation was led by Hafeez Saeed, the Jamaat-ud-Dawa emir currently under house arrest.

"Most of my colleagues are from Jamaat-ud-Dawa," he said, adding that it had 80 volunteers in Mardan district. He refused permission for an interview with the bearded young volunteers around him. "No need to speak with anyone else," he said.

Amir Rana, an expert on jihadi groups, said that Falah-i-Insaniat was the new name for Khidmat-i-Khalq, the relief wing of Jamaat-ud-Dawa, which the US designated as a terrorist organisation in 2005.

Local media reports said the FIF name was first used to stage a protest rally against the Indian presence in Kashmir in Lahore last February. It also ran relief operations for the victims of an earthquake in Baluchistan province last November.

"They have changed their identity and are continuing their humanitarian activities," said Rana.

It may seem ironic that the people of Swat, escaping an area where an experimental peace deal with extremists has gone horribly wrong, should be welcomed to safety by a group with links to the Mumbai attacks.

But it highlights the ambiguities of the Pakistani government's effort to dismantle Jamaat-ud-Dawa, which Rana said has "not been serious".

The difficulty is that Jamaat-ud-Dawa's charity operations – running schools, hospitals and relief organisations – are considered to be legitimate humanitarian activities. Often they are better organised and funded than comparable government services.

Closing them down would also hurt their beneficiaries. After Jamaat-ud-Dawa was banned in December, a group of Pakistani Hindus held a street protest against the UN action.

Another factor is the group's close links to Pakistan's powerful security establishment. After the Kashmir earthquake in 2005,President Pervez Musharraf praised Jamaat-ud-Dawa's impressive relief operation.

These days, Rana said, Jamaat-ud-Dawa's activities in Punjab were controlled directly by the government, but its aid operations in Baluchistan and the North-West Frontier province continued to operate autonomously.

For many, Jamaat-ud-Dawa is seen as an extension of the powerful ISI intelligence agency. Despite its high profile, the FIF operation in Mardan has not been highlighted in the Pakistani press.

In Sher Gur, the FIF camp is conspicuously well funded and organised – particularly in comparison with the chaotic efforts of the government.

"We are very grateful to them," said Bakht Nazar, a labourer from Lower Dir, as he hunkered down over a plate of rice at the FIF camp in Sher Gur, pausing between mouthfuls to rail against army shelling of civilian buildings in his home area.

Watching over him was Enamullah, a burly, thick-bearded volunteer in his 40s who leaned on a walking stick. "We don't seek media attention but we have a strong image among the masses. Whatever we are doing is only for God," he said, pointing to the sky.